Many of the current shortcomings in diagnosis, prognosis, risk stratification and treatment of disease can be approached through the identification of the molecular mechanisms underlying a disease and through the discovery of nucleotide sequences (or sets of nucleotide sequences) whose expression patterns predict the occurrence or progression of disease states, or predict a patient's response to a particular therapeutic intervention. In particular, identification of nucleotide sequences and sets of nucleotide sequences with such predictive value from cells and tissues that are readily accessible would be extremely valuable. For example, peripheral blood is attainable from all patients and can easily be obtained at multiple time points at low cost. This is a desirable contrast to most other cell and tissue types, which are less readily accessible, or accessible only through invasive and aversive procedures. In addition, the various cell types present in circulating blood are ideal for expression profiling experiments as the many cell types in the blood specimen can be separated if desired prior to analysis of gene expression. While blood provides a very attractive substrate for the study of diseases using expression profiling techniques, and for the development of diagnostic technologies and the identification of therapeutic targets, the value of expression profiling in blood samples rests on the degree to which changes in gene expression in these cell types are associated with a predisposition to, and pathogenesis and progression of a disease.
In particular, acute allograft rejection diagnosis and monitoring may benefit from such an approach. Current diagnosis and monitoring of acute allograft rejection is achieved through invasive allograft biopsy and assessment of the biopsy histology. This approach is sub-optimal because of the expense of the procedure, cost, pain and discomfort of the patient, the need for trained physician operators, the risk of complications of the procedure, the lack of insight into the functioning of the immune system and variability of pathological assessment. In addition, biopsy can diagnose acute allograft rejection only after significant cellular infiltration into the allograft has occurred. At this point, the process has already caused damage to the allograft. For all these reasons, a simple blood test that can diagnose and monitor acute rejection at an earlier stage in the process is needed. Allograft rejection depends on the presence of functioning cells of the immune system.
There is an extensive literature supporting the role of leukocytes, e.g., T- and B-lymphocytes, monocytes and granulocytes, including neutrophils, in a wide range of disease processes, including such broad classes as cardiovascular diseases, inflammatory, autoimmune and rheumatic diseases, infectious diseases, transplant rejection, cancer and malignancy, and endocrine diseases. For example, among cardiovascular diseases, such commonly occurring diseases as atherosclerosis, restenosis, transplant vasculopathy and acute coronary syndromes all demonstrate significant T cell involvement (Smith-Norowitz et al. (1999) Clin Immunol 93:168-175; Jude et al. (1994) Circulation 90:1662-8; Belch et al. (1997) Circulation 95:2027-31). These diseases are now recognized as manifestations of chronic inflammatory disorders resulting from an ongoing response to an injury process in the arterial tree (Ross et al. (1999) Ann Thorac Surg 67:1428-33). Differential expression of lymphocyte, monocyte and neutrophil genes and their products has been demonstrated clearly in the literature. Particularly interesting are examples of differential expression in circulating cells of the immune system that demonstrate specificity for a particular disease, such as arteriosclerosis, as opposed to a generalized association with other inflammatory diseases, or for example, with unstable angina rather than quiescent coronary disease.
A number of individual genes, e.g., CD11b/CD18 (Kassirer et al. (1999) Am Heart J 138:555-9); leukocyte elastase (Amaro et al. (1995) Eur Heart J 16:615-22; and CD40L (Aukrust et al. (1999) Circulation 100:614-20) demonstrate some degree of sensitivity and specificity as markers of various vascular diseases. In addition, the identification of differentially expressed target and fingerprint genes isolated from purified populations of monocytes manipulated in various in vitro paradigms has been proposed for the diagnosis and monitoring of a range of cardiovascular diseases, see, e.g., U.S. Pat. Nos. 6,048,709; 6,087,477; 6,099,823; and 6,124,433 “COMPOSITIONS AND METHODS FOR THE TREATMENT AND DIAGNOSIS OF CARDIOVASCULAR DISEASE” to Falb (see also, WO 97/30065). Lockhart, in U.S. Pat. No. 6,033,860 “EXPRESSION PROFILES IN ADULT AND FETAL ORGANS” proposes the use of expression profiles for a subset of identified genes in the identification of tissue samples, and the monitoring of drug effects.
The accuracy of technologies based on expression profiling for the diagnosis, prognosis, and monitoring of disease would be dramatically increased if numerous differentially expressed nucleotide sequences, each with a measure of sensitivity and specificity for a disease in question, could be identified and assayed in a concerted manner. Using the expression of multiple genes (gene sets) for diagnostic applications can help overcome assay and population variability. PCT application WO 02/057414 “LEUKOCYTE EXPRESSION PROFILING” to Wohlgemuth identifies one such set of differentially expressed nucleotides.
In order to achieve this improved accuracy, the sets of nucleotide sequences once identified need to be validated to identify those differentially expressed nucleotides within a given set that are most useful for diagnosis, prognosis, and monitoring of disease. The present invention addresses these and other needs, and applies to transplant rejection for which differential regulation of genes, or other nucleotide sequences, of peripheral blood can be demonstrated.